function validateForm(form)
		{
		var check="";
		check+=validateUsername(form.login);
		check+=validatePass(form.password);
		check+=validateEmail(form.email);
		check+=validateEmpty(form.fname);
		check+=validateEmpty(form.lname);
		
			if(check!="")
			{
			alert("Some field is incorrect:\n"+check);
			return false;
			}
			document.getElementById("mesg").innerHTML = "Login Sucess";
			return true;
	

	}
function validateEmpty(fld) {
		    var error = "";
		  
		    if (fld.value.length == 0) {
		        fld.style.background = 'Yellow'; 
		        error = "The required field has not been filled in.\n"
		    } else {
		        fld.style.background = 'White';
		    }
		    return error;   
		}
		
<!-->		
function validateUsername(fld) {
    var error = "";
    var illegalChars = /\W/; // allow letters, numbers, and underscores
     if (fld.value == "") {
        fld.style.background = 'Yellow'; 
        error = "You didn't enter a username.\n";
    } else if (fld.value.length < 5) {
        fld.style.background = 'Yellow'; 
        error = "The username is the wrong length at least 8 characters.\n";
    } else if (illegalChars.test(fld.value)) {
        fld.style.background = 'Yellow'; 
        error = "The username contains illegal characters.\n";
    } else {
        fld.style.background = 'White';
    }
    return error;
}
<!--->
function validatePass(fld) {
    var error = "";
    var illegalChars = /[\W_]/; // allow only letters and numbers 
 
    if (fld.value == "") {
        fld.style.background = 'Yellow';
        error = "You didn't enter a password.\n";
    } else if (fld.value.length < 8)  {
        error = "The password is the wrong length. \n";
        fld.style.background = 'Yellow';
    } else if (illegalChars.test(fld.value)) {
        error = "The password contains illegal characters.\n";
        fld.style.background = 'Yellow';
    } else if (!((fld.value.search(/(a-z)+/)) && (fld.value.search(/(0-9)+/)))) {
        error = "The password must contain at least one numeral.\n";
        fld.style.background = 'Yellow';
    } else {
        fld.style.background = 'White';
    }
   return error;
} 
function trim(s)
{
  return s.replace(/^\s+|\s+$/, '');
} 

function validateEmail(fld) {
    var error="";
    var tfld = trim(fld.value);                        // value of field with whitespace trimmed off
    var emailFilter = /^[^@]+@[^@.]+\.[^@]*\w\w$/ ;
    var illegalChars= /[\(\)\<\>\,\;\:\\\"\[\]]/ ;
    
    if (fld.value == "") {
        fld.style.background = 'Yellow';
        error = "You didn't enter an email address.\n";
    } else if (!emailFilter.test(tfld)) {              //test email for illegal characters
        fld.style.background = 'Yellow';
        error = "Please enter a valid email address.\n";
    } else if (fld.value.match(illegalChars)) {
        fld.style.background = 'Yellow';
        error = "The email address contains illegal characters.\n";
    } else {
        fld.style.background = 'White';
    }
    return error;
}